The present invention relates to a process for preparing a ketone from an aliphatic or cycloaliphatic compound E containing at least one epoxy group, and to a process for synthesizing lactams.
The opening of oxirane rings with acidic or basic oxides has been described (V. S. Joshi, N. P. Damodaran, S. Dev, Tetrahedron 1971, 27, 459-474; K. Arata, K. Tanabe, Bull. Chem. Soc. Jpn. 1980, 53, 299-303; K. Arata, H. Nakamura, Y. Nakamura, Bull. Chem. Soc. Jpn. 1994, 67, 2351-2353). From a compound containing epoxy groups, such as monoepoxycyclododecane (CDAN epoxide), the allyl alcohol (3-cyclododecenol; CDENOL) may first be obtained. This may be followed by the conversion to the ketone (cyclododecanone; CDON).

The problem which occurs in this two-stage reaction is that, as well as the cyclic allyl alcohol, dehydrated dienes or dimers form as by-products.
A selective conversion of the epoxide to the ketone was reported by Chemyshkove and Mushenko (Chemyshkove, F. A.; Mushenko, D. V. Neftekhimiya 1976, 16, 250-4). For this purpose, the epoxides were reacted in a hydrogen atmosphere over palladium and rhodium catalysts which were supported on alumina or carbon. With complete conversion of the reactant, the ketones were obtained with yields exceeding 80%.
EP-A-1090900 describes the reaction of CDAN epoxide to give a mixture of CDON and cyclododecanol (CDOL). For this purpose, platinum group metals, an inert support and a promoter are used. The reactions proceed in a hydrogen atmosphere.
EP-A-1018498 describes reaction of cyclic epoxides with hydrogen and platinum group metals in a hydrogen atmosphere to obtain a ketone/alcohol mixture. The hydrogen pressure is at least 1 bar. The document teaches that lower pressures would require an excessively long reaction time.
The problem thus addressed was that of adapting the production of ketones from epoxides such that a high proportion of ketone may be obtained with a low alcohol content. In addition, by-products, especially unsaturated by-products, should form in a minimum concentration. Moreover, the reaction should be of lower technical complexity in comparison to conventional methods previously described. The two-stage reaction to give the ketone should be possible without isolation of the intermediate allyl alcohol and the reaction time should correspond to the time required in conventional processes.